Just noticed that in British divisions, these units have a platoon sized estab despite being called companies. Presumably this is a mistake. A British infantry division was supported by a machine gun battalion comprising one heavy mortar company and three machine gun companies.

No problem, thanks - in the game the machine guns have been incorporated into the infantry coys. The 4.2" hvy mor coys can either be assigned at div level as a whole coy or broken down and assigned as platoons at bde level - I prefer the latter.

Not quite - there were three MG companies - these were usually assigned one per brigade (and then often oe platoon per battalion) in normal cases. But could be massed for attack eg one each flank of the attacking brigades - or all grouped for pepperpots. In the fourth mortar company, the four platoons of heavy mortars were treated similarly - with one big BUT. When attacking they were paired to form a 'mini-company' of eight mortars and used as mortar counter-bombardment weapons. Note that they were not usually used for direct infantry support as the blast radius was large and the mortars lacked the precision of 25pdr guns. They were mich more useful as area suppression weapons best fired at about 4,000 yards.